It is proposed to critically evaluate histochemical methods for the detection and localization of receptors for both steroid and protein hormones in human prostatic tumour tissue and to assess the data in relation to the patient's clinical response to endocrine therapy. Immunocytochemical techniques will be used to localize endogenous protein hormones and their binding sites. The topography of steroid hormone binding site will be examined using fluorescein-labelled steroids or steroid conjugates in relation to analyses for nuclear and cytosolic androgen receptor levels determined by routine biochemical procedures. Normal rat prostate and the Dunning R3327 rat prostate tumour tissue will also provide an additional means of evaluating these histochemical procedures. Furthermore, the biochemical nature of the binding moieties of the fluorescent-labelled steroids will be studied in depth, as an integral part of the research programme, using subcellular fractionation, ion-exchange and gel exclusion chromatography. The British Prostate Study Group's criteria of response to therapy will be used for the work, together with the UICC (TNM) classification of clinical data.